Compressed-air-powered　vehicles　with　advantages　of　environmentally　simple　and　non-spark　operation,　good　maintenance,　and　convenient　operation　have　drawn　the　attention　of　scholars.　However,　a　vehicle　driven　by　compressed　air　alone　cannot　be　a　viable　alternative.　In　this　paper,　an　auxiliary　power　system　based　on　a　pneumatic　motor　used　for　compressed-power　vehicle　is　proposed.　First,　the　test　rig　of　the　auxiliary　power　system　is　established　based　on　a　pneumatic　motor.　The　effects　of　key　operating　parameters　on　the　performance　of　the　pneumatic　motor　are　investigated　by　experimental　analysis　and　using　the　control　variable　method.　The　step　response　characteristics　of　the　pneumatic　motor　and　the　relationship　between　rotation　speed,　torque,　power　output,　and　volume　flow　rate　are　studied.　The　uncertainties　of　the　power　output　and　energy　efficiency　of　the　pneumatic　motor　are　analyzed.　Experimental　results　show　that　the　power　output　and　energy　efficiency　of　the　pneumatic　motor　first　increase　and　then　decrease　with　the　increase　of　torque.　The　energy　efficiency　of　the　pneumatic　motor　reaches　the　maximum　value　of　approximately　62%.　The　power　output　of　the　pneumatic　motor　reaches　the　maximum　value　of　approximately　410　W.　The　pneumatic　motor　is　more　feasible　to　be　considered　an　auxiliary　system　of　compressed-air-powered　vehicle.　(c)　2021　Elsevier　Ltd.　All　rights　reserved.